1. Field of the Invention
The present invention relates to an anti-fogging coating film having excellent weather resistance, transparency and adhesion to a base material, anti-fogging articles comprising a base material such as glass, plastic, metal or mirror and the anti-fogging coating film provided thereon, and a composition for forming the anti-fogging coating film.
2. Related Background Art
The weak point of articles making use of a base material such as glass, plastic, metal or mirror is that fine waterdrops adhere to their surfaces when they are used at a high-temperature and high-humidity place or in an environment with large temperature or humidity variations, and so they are fogged up.
A known method for inhibiting fogging consists of forming an anti-fogging layer containing a hydrophilic polymer on the surface of glass, plastics, metal, mirror, etc., with the hydrophilic polymer including polyvinyl alcohol, polyethylene-imine, polyvinyl butyral, etc.
An anti-fogging layer containing a hydrophilic polymer has poor water resistance and undergoes deterioration by sunlight and hence creates a problem of weather resistance. On the other hand, it has been known to coat a base material with a composition containing colloidal silica and a surfactant as a method for enhancing water resistance. However, such a method has involved problems with transparency and the anti-fogging property.
It is also known to add an ultraviolet absorbent such as a benzotriazole compound for the purpose of improving the weather resistance. However, such a method deteriorates transparency and so on, though the weather resistance is improved.
As described above, in such prior art techniques, an anti-fogging coating film having high water resistance and satisfactory weather resistance and transparency has not been yet obtained.